OBJECTIVES: We have found that cell membranes of many kinds of tumor cells have the ability to activate complement systems in the absence on antigen-antibody reaction and that the ability can be generated by infection of Moloney Sarcoma virus fraction. Therefore I am going to study the mechanism of the generation of such membrane ability and the possible role of such membrane ability in the pathogenesis in cancer as well as autoimmune disease. METHODS: 1) Generate the complement activating ability on cultured cells by infecting with viruses and study the mechanisms involved. 2) In the course of development of chemically or virus induced tumors in experimental animals, the appearence of cells which have ability to activate complement will be analyzed by use of immunofluorescent technique. 3) Tumor cells from cancer patients as well as specimens from patients suffering from virus infection or autoimmune disease will be examined in the membrane ability to activate complement using immunofluorescent technique and radioimmunotitration of fixed C3 after treatment with diluted serum in Mg ion-EGTA buffer. 4) The reaction mechanism of cell membrane in activation of complement will be analyzed by use of purified factors in the alternate pathway of complement which will be prepared after sequential column chromatographies on CM52, DE52 and Sephadex G200 as well as electrophoresis. 5) Substances which activate complement on cell membranes will be tried to purify in order to know the chemical nature of the substance. The knowledge will contribute to develop some new methods to treat patients who may have trouble with complement activating pathogenic cells.